In public sales premises, the loss of goods through shoplifting is significant, especially where high-priced clothing is accessible to the general public for try-on or examination. Since clothing can constitute expensive articles and personal supervision of each individual having access to garments on racks, shelves and tables is not practical, it has been proposed to prevent losses resulting from shoplifting by means of various monitoring systems.
For example, it is not uncommon to affix to a garment a "signal transmitter" containing a continuously effective signal emitter, e.g. a source of radioactivity, an induction coil, or a remotely activatable output generator, which can cooperate with a receiver or monitoring device at the entrance or exit of the premises to generate an alert when a garment carrying the transmitter passes through the portals. The sales person, cashier or other member of the staff is generally equipped with a special tool for removing the signal transmitter after the sales transaction has been completed so that the garment may be free from the transmitter when legitimately removed from the premises.
While this system has been highly successful in preventing the removal of garments with signal transmitters, it does not solve the problem of theft involving the removal of the signal transmitter from the garment. In spite of the fact that such removal is difficult without special tools, the ingenuity of the thief has not been thwarted by the devices used heretofore. As a result a thief taking the garment into a dressing room or some other relatively concealed location may be capable of removing the transmitter and leaving the premises with the garment without the transmitter. Since the monitoring devices, which respond only to the proximity of the transmitter, will not be activated in these cases, the conventional systems are ineffective against theft in this manner.
The removal of the transmitter is common with professional thieves so that, against such persons, the conventional system is no protection.